Semiconductor process chambers experience high operational temperatures, for example, in the range of 650-1150° C., in the uniform epitaxial deposition of a material on a substrate such as a wafer. Radiative lamp heating in such chambers and laminar cross-flow design for uniform deposition requires accurate positioning and centering of a wafer in the chamber. A wafer rotation and lift mechanism in the chamber requires extensive set-up for accurate positioning of the wafer during process. During wafer processing, a wafer is positioned on a susceptor. If the susceptor position is incorrect, for example, if it is not level, off-center or exhibits wobble, the positional inaccuracy can cause non-concentric or even an “out-of-pocket” wafer placement. Also, high wafer transfer temperature, desired for high throughput, may cause thermal shock and deformation to the wafer. This can lead to wafer positional inaccuracies on a robot-blade or susceptor, resulting in non-uniform film thickness, slip-line defects or even wafer breakage in the chamber which can prove very costly to the customer. Current practice to solve these problems relies on efforts to adjust positions and limit transfer temperatures without the ability to see the wafer during process.
Improved and automatic monitoring of substrate positioning, and adjustment to warping or deformation of a substrate from camera images can greatly improve the efficiency of the fabrication process of the processing chamber. Accordingly improved methods and apparatus for substrate monitoring by providing a monitoring system that monitors the position of the wafer from the inside of a high temperature process chamber are desired.